Fix ommissions in window scrolling commands that ought to clear vscroll

Fix ommissions in window scrolling commands that ought to clear vscroll

* src/window.c (Fdelete_other_windows_internal)
(window_scroll_for_long_lines, Frecenter, Fmove_to_window_line):
Reset window vscroll, or, if force_start be set, just
preserve_vscroll_p, after moving window start to a position
computed from iterators for the window in question, so that
vscroll may be reliably reset again after the conditions for
redisplay's doing the same were corrected.  (bug#70386)